We turned our microwavable play dough recipe into hot chocolate play dough. I started by mixing 2 cups flour, 1 cup salt, 2 cups water, 1 Tbsp cream of tarter, 2 Tbsp oil, 1 tsp vanilla, and the contents of 3 k-cup hot chocolates. (Cocoa would work too if you don't have hot chocolate on hand.) I added a couple of drops of brown food coloring to darken it even more.
Microwave for 1 minute. Stir. Microwave for another minute. Stir. Continue the process until most of the moisture is absorbed. It took 4 minutes and 30 seconds total before I pulled mine out and started kneading it. (It will be hot. Make sure you let it cool before the kids play with it.)
They had a great time adding "marshmallows" and having a little hot chocolate party.